2004 Ford Focus: Fuel pump is not pumping fuel to engine

Maintenance/Repairs
1

I’ve replaced the fuel pump, relay, drive module, and the filter. The fuel pump still refuses to switch on when I go to start the vehicle.

2

You didn’t happen to trip the inertia switch that cuts power to the fuel pump?

Tester

3

I’ve already reset the switch. There’s power going to the pump, but its just not pumping.

4

Is it possible there’s a plugged line? Pump comes on for just a split second, then the line is pressurized and it shuts off. They don’t just keep pumping fuel forever - they pressurize and stop.

5

Nah, not a line or anything. The pump literally doesn’t start. We’ve tried it with two pumps already, and neither came on.

6

Then check for a bad ground. It’s the black wire to the fuel pump.

Tester

7

The fuel pump is ground side controlled by the Fuel Pump Driver Module (FPDM) When verifying the ground, verify the ground to the driver module as Tester indicated.

The FPDM supplies a variable ground signal to the fuel pump in order to control the pump speed and hence the fuel pressure. (Yes the fuel pressure is variable depending engine operating conditions.) The pressure is determined by the PCM watching the input from the Fuel Rail Pressure (FRP) sensor. The PCM has a desired target fuel pressure based on the intake manifold pressure, the higher the manifold pressure, the harder the PCM will request the FPDM drive the fuel pump.

In rare cases, the FRP sensor will report erroneously excessive pressure. In this case the PCM incorrectly believes that the fuel pressure is higher than required and shuts the fuel pump off. The FRP sensor is on the fuel rail and can be unplugged electrically. If unplugged (FRP) the fuel pump will be commanded on at a default value, you can check to see if the pump turns on and whether the vehicle runs. If the pump runs, you have a circuit fault to the FRP or the sensor is shot.

If the pump still refuses to run, there are a couple of other issues that can be present:

  • The ignition switch power is supplied to the FPDM to power the module and splices off to power the pump itself. This needs reverified. If the Driver module has no power supplied, it will never attempt to run the pump. You need to load test the circuit.
  • The PCM and FPDM communicate via two wires… The fuel pump COM circuit and the Fuel Pump Monitor circuit. These circuits pass between the PCM and the FPDM and will need verified. IF the COM circuit (blk/wt) circuit is open, the FPDM will never see an on signal from the PCM and the pump will never run. (Signal is a duty cycle 5-50 percent is a valid on request. 5% equals 10% pump request, 50% command is 100% on the pump, remember the pressure control is fully variable)
  • Circuits between the Driver module and pump could be compromised. Verify continuity and pin fit at related electrical connectors.
8

This could indeed be confusing to debug from the comments in the posts above. It would look like the pump is getting power at its 12 volt input, but in fact the ground isn’t being connected. And w/no ground, no current will flow.

I’d be inclined to measure the current flow in the power wire going to the pump to assess if the ground is being connected or not. It’s probably quite a bit of current, 10 amps or more maybe, so an ordinary current meter might not work and could be damaged if wired up in-line. I have an inexpensive DC current meter I got at Sears years ago that senses the magnetic field from the current flowing in the wire and you just put the wire in a little channel in the meter and read how much the needle deflects.

One other idea: OP should be aware that on many fuel injection systems the computer must sense the engine is rotating before it will turn on the pump. This is a safety feature, to prevent the pump from pouring fuel in the event of an accident. So if you have a problematic crank or cam sensor, that would make the computer think the engine isn’t rotating, and that could cause this symptom.

9

George,

The computer runs the fuel pump for a second or two to pressurize the fuel system when the ignition is turned on, before the engine is even started.

Tester

10

Tester. I see what you mean. This applies for the Focus I presume. That wasn’t the case with my VW Rabbit. I do think the Corolla fuel pump will come on briefly even if the engine isn’t running. But it won’t run for long that way. If the OP is certain the pump is not coming on at all, even briefly, it wouldn’t be the engine rotation sensor problem in this case.